Heterobasidion annosum (Polyporus annosus, Trametes radiciperda, Fig. [169]) is characterized by its Aspergillus-like conidiophores. It is a parasite on the Pine, Fir, Birch, Beech, etc., and is the chief cause of a root-disease (red-rot) in Pines and Firs; the fruit-bodies develope a large number of basidiospores; they may be very large and are found just beneath the surface of the soil (on living or dead roots), and exposed to the air (on felled stems and roots, in Scandinavia).
Ptychogaster has cushion-like fruit-bodies, which consist chiefly of chlamydospore-chains, formed of ellipsoidal spores, which alternate with short hyphæ having transverse septa and clamp-connections. The hymenial portion is limited to a small group of tubes. Pt. albus (Oligorus ustilaginoides) grows on stumps of Conifers and forms irregular cushions, at first white and later on brown, which consist almost entirely of chlamydospores.
Boletus (Fig. [171]) has a fleshy fruit-body resembling a common Mushroom, with central stalk. The layer of tubes is easily detached from the pileus, and the tubes are easily separable from one another. They grow on the ground in woods. Edible species are: B. edulis, with thick, reticulate stalk; B. scaber, with thin stalk and rough pileus; B. luteus, with a ring on the stalk. B. luridus is poisonous, its tubes have red openings, and the flesh turns quickly blue when broken and exposed to the air.
Fistulina hepatica (Beef-steak Fungus), has a red, fleshy, edible fruit-body, with red juice. The tubes are individually distinct; conidia are also developed. Grows on old Oaks.
Merulius lacrymans (“Dry-rot”) has a resupinate fruit-body with white, cotton-like border, and the remaining portions covered by reticulate, ramified veins of a rust-brown colour. In favourable vegetative conditions it is fleshy and exudes large drops of water—hence its specific name and also the name “Tear Fungus.” The mycelium is at first colourless, and then yellow-brown; when dry it is tough and leathery. It destroys the timber in damp houses, extends far and wide over boards and beams and even over the masonry, giving rise to a disagreeable smell in the rooms in which it lodges. In woods the Fungus lives on Pine-stems. It is brought from the forest on the logs of timber, and is distributed from log to log by the mycelium and the basidiospores. The living mycelium can be recognised by the clamp-connections shooting out branches. The basidiospores are often ejected a distance of a metre; they are elliptical (10–11µ long and 5–6µ broad), and germinate easily on damp wood, or in fruit-juice which has been neutralized with urine or alkaline carbonates.
Dædalea (Labyrinth Fungus), has bracket-like, corky fruit-bodies with irregularly-folded plates or discs on the under side. It forms a transition to the Agaricaceæ. D. quercina is frequent on Oak-stumps.
Fig. 171.—Boletus edulis (about ¼th): b longitudinal section of a portion of the pileus.
Order 6. Agaricaceæ (Mushrooms, Toadstools). The hymenophore consists of knife-like plates (lamellæ, gills), which are situated on the under side of the umbrella-like pileus of the fruit-body, and radiate from the central stalk. Those which are first formed extend from the edge of the pileus to the stalk; those formed later reach only a longer or shorter portion of this distance, according to their age. In structure the lamellæ (Fig. [174]) consist of a central mass of hyphæ, the trama, continuous with the hyphæ of the pileus; these terminate in a layer of shorter cells, the subhymenial layer, immediately beneath the hymenium which is composed of basidia and paraphyses. In a few species, but not in the majority, the lamellæ are branched, and in some they are decurrent. A few have the stalk placed excentrically, or it may be entirely absent.
